Saturday, 15 February 2014

Burgess 3.0

Waptia fieldensis  one of the stranger creatures
from the 505 million year old Burgess Shale
505 million years ago a massive underwater avalanche of mud and sediment in the Burgess Shale entombed a collection of the Earth's most unique animals, trapping them in the fossil record.

Some were relatives of modern day groups such as crustaceans or molluscs. Others were failed experiments in the history of life, extinct phyla which were completely unknown to science until just a few decades ago.

What makes them important, however, is that they are a record of one of the most important events in the history of life, the Cambrian Explosion. The diversity and biological ingenuity of life increased tenfold, with complex body designs, brains, eyes common to all modern animal groups. For a while the Burgess Shale was the only existing fossil site which captured the scale of this event. Then in 1984 a hoard of fossils collected from the 512 million year old Maotianshan Shale showed that we had underestimated the sheer size of the Cambrian Explosion; with hundreds of new species described in just a few years after the locality's discovery.

A fossil from the 512 million year old Maotianshan Shales
The Maotianshan site has the added bonus of preserving delicate, internal soft tissue, revealing complex internal anatomies from digestive tracts to nervous systems.

A number of smaller sites around the world, in particular Australia, have yielded similarly well preserved fossils from the Cambrian Explosion, but none equal to the quality or quantity seen in Maotianshan specimens. For this reason it has been described as the Burgess Shale of the East or the second Burgess Shale (Burgess 2.0). It is not an undeserved tag.

Yet a third locality is set to propel our understanding of the Cambrian Explosion further still. Just 42 kilometres away from the hallowed Burgess site, a team led by Professor Jean Bernard Caron, famous for his work on Burgess specimens, have uncovered fossils from the Marble Canyon formation in Canada's Kootenay National Park. While geologically similar to the Burgess Shale, it tells its own unique story.

Caron's team actually came across the site in mid 2012. They had examined the geology in British Columbia, looking for similarities to the Burgess Shale. They followed a breadcrumb trail of fragmented fossils and shale up a steep scree slope until they found the source. 'We were already aware of the presence of some Burgess Shale fossils in Kootenay National Park,' said Dr. Robert Gaines from Pomona College. 'We had a hunch that if we followed the formation along the mountain topography into new areas with the right rock types, maybe, just maybe, we would get lucky though we never in our wildest dreams thought we'd track down a motherload like this.'

Jean Bernard Caron extracting fossils from the Marble Canyon shales.
This is remarkably similar to how the original Burgess site was discovered by Charles Doolittle Walcott, in the early 20th century. Like Caron's team, Walcott followed a trail of fossils and rock fragments up the sides of Mount Burgess in the Yoho National Park until he found the 2 foot thick rock seam.

In just 15 days Caron's team collected thousands of specimens, 50 of which were new species. By comparison over a hundred years of research at Burgess has yielded just 200 new species amongst the tens of thousands collected by Walcott between 1910 and 1924 and later expeditions in the 1970s and 1980s. Even the Kootenay specimens which do not represent novel genera are of importance as there is a significant overlap with species seen in the Maotianshan Shales. This indicates that the temporal and geographical range of Burgess type fauna has most likely been underestimated. Many of the Marble Canyon fossils preserve structures which were previously unrecorded or absent in Burgess specimens.

The Marble Canyon site in Canada's Kootenay National
Park is bound to throw up surprises in the coming years
'This new discovery is an epic sequel to a research story that began at the turn of the previous century. There is no doubt in my mind that this new material will significantly increase our understanding of early animal evolution,' said Dr. Jean-Bernard Caron from the University of Toronto. 'The rate at which we are finding animals, many of which are new, is astonishing, and there is a high probability that we'll eventually find more species here than at the original Yoho National Park site and potentially more than from anywhere else in the world.'

Marble Canyon is set to become the third Burgess Shale (Burgess 3.0) with a wealth of new discoveries. The Cambrian Explosion is the reason why life looks the way it does today. Understanding the event and its triggers has been of importance since the Cambrian fossils were first recognised. The Burgess Shale initiates the story, the Maotianshan shows us we have barely scratched the surface.